1. Field of the Invention
The present invention relates to a magnetic head comprising a single pole type head for perpendicular magnetic recording and a process of fabricating such a head.
2. Description of Related Art
In recent years, there has been a continuing need for hard disk drives (HDDs) with larger capacity and smaller dimensions which are magnetic recording/reproducing devices employed as external recording devices for data processing equipment such as computers. Accordingly, HDD manufacturers mainly pour their efforts into improving the areal recording density of HDD heads to meet such need. However, in order to achieve higher density recording performance with conventional longitudinal magnetic recording, the recording layer thickness must be made thinner, because a demagnetizing field comes to have maximum energy in the region of magnetization-reversal transition in a magnetic hysteresis (MH) loop of magnetization for recording on a recording medium. In consequence, a problem is presented that thermal disturbance resulting from the demagnetizing energy erases recorded data. Meanwhile, for perpendicular magnetic recording in which the direction of magnetization for recording is the direction of thickness of a medium, it is relatively less needed to thin the thickness of the medium, because the demagnetizing field comes to have minimum energy in the region of magnetization-reversal transition in the MH loop, and, thus, high density recording performance is easy to achieve.
When recording a signal on a perpendicular recording medium with a magnetic head for perpendicular magnetic recording, or namely, a perpendicular magnetic head (single pole type head), an electric signal is converted into a magnetic signal by coils and magnetic flux is excited in a main pole and a return pole. Part of the magnetic flux travels from the return pole and through the main pole and passes through the recording layer of a recording medium. The magnetic flux passes through a soft magnetic under layer under the recording layer and returns to the return pole, thus forming a closed loop. The return pole is used to return magnetically and efficiently the magnetic flux generated from the main pole and passed through the recording layer and under layer of the recording medium. Through this magnetic flux flow, magnetization takes place on the perpendicular recording medium, thus recording the signal on the medium. An example of such a magnetic head is reported in the Journal of the Magnetics Society of Japan, Vol. 24, 335–338 (2000).
With the improvement of areal recoding density of the above-mentioned perpendicular magnetic recording heads, it is desired that the width of a recording track should be reduced. However, reduction in the recording track width causes decrease in a magnetic field which is generated from the tip of the main pole and across the magnetic recoding medium. Thus, the thickness of the main pole should be thicker to prevent the decrease in the magnetic field. Meanwhile, a magnetic disk drive must perform recording and reproduction in a wide range of inner to outer concentric circular tracks of a magnetic recording medium. However, its magnetic head performs write and readback operation to/from the concentric circular tracks of the magnetic recording medium at a skew angle of about 0 to 15° from the tangent to the revolving direction of the magnetic recording medium. If the main pole has a rectangular air-bearing surface, the recording track width cannot be reduced. Therefore, methods of tailoring the magnetic pole shape for narrower tracks by making the track width of the leading side of the main pole narrower than that of the trailing side thereof have been proposed.
Examples of methods in which a magnetic head is fabricated such that the track width of the leading side of the air-bearing surface of the main pole is narrower than that of the trailing side thereof are given below. JP-A No. 92821/2002 discloses a method of forming a main pole having an inverted trapezoid shape, which comprises forming a resist frame on a non-magnetic insulator layer, forming a trench on the non-magnetic insulator layer by reactive ion etching (RIE), plating the surface with a magnetic layer, and chemical mechanical polishing (CMP). JP-A No. 197609/2002 discloses a method of forming a main pole having an inverted trapezoid shape, which comprises forming a resist frame on a plating under layer and plating the surface with a magnetic layer and a non-magnetic layer. JP-A No. 208112/2002 discloses a method of forming a main pole having an inverted trapezoid shape, which comprises depositing a non-magnetic layer on a magnetic layer, forming a resist frame, plating, and dry etching.
[Non-Patent Document 1] Journal of the Magnetics Society of Japan, Vol. 24, 335–338 (2000)
[Patent Document 1] JP-A No. 92821/2002
[Patent Document 2] JP-A No. 197609/2002
[Patent Document 3] JP-A No. 208112/2002